Thai Army officers patrolling the Cambodian border said the heaviest fighting of the current dry season occurred Monday at the sprawling refugee encampment at Ampil, a mile inside Cambodia and 25 miles northeast of the major Thai border town of Aranyaprathet.

At least 85 civilians, many of them women and children, have been killed or wounded in the Vietnamese attacks on Ampil that began Sunday, military sources said.

The Vietnamese timed their infantry assault to coincide with Cambodian New Year over the weekend and caught celebrating fighters in the anticommunist Khmer People's National Liberation Front unprepared to fight, a source close to the KPNLF said.